Depends on what he is back talking about. You can teach him a better way to use his words and to make requests or adjustments.
Children need to feel like they have a little control at times. Not EVERYTHING can be a negotiation, but sometimes, at least giving a heads up, lets the child have a small transition. They also like being praised for doing things when asked.
This will also be a way to remind them, "This time we will have to do this right now. Next time maybe you can play longer. "
I Taught our daughter, to answer politely. "Yes, ma'am". Or "may I have 1 more minute?"
At a meal time..
"It is bad manners to say food is yucky."
"Instead we say, no thank you."
"It hurts my feelings that I cooked this just for you and you will not just try it?"
"I wish you would be a Brave taster and just try this."
" I understand you are afraid you will not like this, but I used to be afraid of some foods, but they are really good."
"I like how you tried that fish!"
"Wow, you are a brave taster."
Transitions help. I also gave our child a heads up.
"In 5 minutes, you will need to start putting your toys in the box".
"In 5 minutes we will be leaving this party, go and play one more time on the swings."
"I liked how you did not whine when it was time to leave."
"I really need you to be my big helper, and put on your coat." "Thank you, I like when you put your own coat on."
I made sure to help her also explain why she did not want to do something, so she could communicate her needs. I also taught her some solutions and options.
"I can tell you are really enjoying coloring, but we need to start getting ready now. "How about you finish your coloring when we get home?" Or
"How about we take this picture and your colors to the restaurant and you can finish it?"
It will give him the proper language to explain what he is dealing with, so that he does not just answer with no.
It will feel strange at first, but then it becomes your normal, eventually, you will not have to have all of this conversation, but right now he is still learning how to behave, how to listen and how he needs to respond. He is only 3. He still has a lot to learn about behaviors and proper language to match his feelings.